Fluid-solids contacting methods and apparatus, particularly for use in desiccating organic materials



Dec. 13, 1966 I K H. SEELANDT 3,290,788

FLUID-SOLIDS CONTACTING METHODS AND APPARATUS, PARTICULARLY I FOR USE INDESICGATING ORGANIC MATERIALS Flled July 16, 1964 I 4 Sheets-Sheet lFIG. I

STAGE I THREE PRODUC" DISCHARGE INVENTOR:

KARL H. SEELANDT BY 6m? 6.

ATT'Y 13, I956 K- H. SE'ELANDT 3,290,788

FLUID-SOLIDS CONTACTING METHODS AND APPARATUS PARTICULARLY FOR USE INDESICCATING ORGANIC MATERIALS Flled July 16, 1964 4 Sheets-Sheet 2 48a 4V A ExHAusT 47a I 34 X |4a q l 504 L 7; (3 I I I I 44a STAGE 04 29a,

4 THREE 1 4 \u Y 38a! I 45a l X 464 X 39 1 ll ALTER-- STAGE FOUR ORALTERNATE STAGE THREE PRODUCT DlSCHARGE INVENTOR: KARL H. SEELANDT Dec.13, 1966 K. H. SEELANDT 3, 8

FLUID-SOLIDS CONTACTING METHODS AND APPARATUS, PARTICULARLY FOR USE INDESICCATING ORGANIC MATERIALS Filed July 16, 1964 v 4 Sheets-Sheet 35127965 Two 5 465 0N5 Dec. 13, 1966 SEELANDT 3,290,788

FLUID-SOLIDS CONTACTING METHODS AND APPARATUS, PARTICULARLY FOR USE INDESICCATING ORGANIC MATERIALS Filed. July 16, 1964 4 Sheets-Sheet 4United States Patent FLUID-SOLIDS CONTACTING METHODS AND AP- PARATUS,PARTICULARLY FOR USE IN DES- ICCAT ING ORGANIC MATERIALS Karl H.Seelandt, 900 N. Lake Shore Drive, Chicago, Ill. Filed July 16, 1964,Ser. No. 384,285 42 Claims. (Cl. 34-5) The present application is acontinuation-in-part of an application entitled, Desiccating OrganicMaterials, Serial No. 169,317, filed January 29, 1962, now abandoned.

This invention relates in general to fluid-solids contacting methods andapparatus, and an exemplary embodiment of the invention relates to novelmethod-s and apparatus for desiccating soluble or primarily soluble andinsoluble organic materials in liquid solution.

The removal of water from food and related products in order to preservethem for long periods of time is a concept well known in the art. Sincewater serves as a catalyst for food spoilage, various methods have beenproposed in the past to remove water from food when it is desired tostore the food for a long period. One widely used method is to sprayliquid foodstuff into a lofty tower which is charged with largequantities of circulating hot air that functions to evaporate themoisture from the foodstuff. This method has proved to be undesirable,in that it has necessitated the use of bulky and expensive apparatus.Additionally, the dried product formed by this method also has certainundesirable characteristics, such as, the desiccated particulate solidshave a relatively small, hard and non-porous surface area, and a highbulk density. These characteristics hinder rehydration, and contributeto undesirable agglomeration of the particulates during rehydration.Also, in high temperature spray drying undesirable chemical reactionsoften occur in heat sensitive materials during the atomized liquiddroplets exposure to the circulating charge of hot air. These chemicalreactions contribute to an excessive loss of de sirable volatileconstituents of the foodstuff which are pertinent to flavor and aroma.

To obviate the problems noted above in connection with high temperaturespray drying, it has been proposed in the past to use a freeze dryingmethod wherein the material to be dried is first frozen and then wateris removed by sublimation. Although freeze-drying methods have beenknown to produce a product having more desirable characteristic thanhigh temperature spray drying methods, freeze-drying methods have notmet with wide commercial acceptance since known freeze-drying methodshave been more costly than conventional spray drying, freezing orcanning processes. One of the factors which has rendered knownfreeze-drying processes extremely expensive, has been the practice ofconducting the freezedrying method in a batch type operation. Since itis difficult to obtain a desired volume of production by batch methods,this type of process and apparatus has proved to be commerciallyunacceptable in certain industries. In order to provide the heat forsublimation it has been proposed to use radiation in the infra-redrange. Here tofore these methods have proven unsatisfactory in that theradiation ranges which are presently used function to heat the article,as Well as subliming the ice, so 'that undesirable scorching of theproduct takes place in the later stages of drying when the freeze-frontrecedes into the interior of the product being dried.

A further disadvantage occurs during freeze drying of liquid materialswhich are usually foamed, frozen in a vacuum, and then freeze-dried. Insuch a process the heat for sublimation is supplied either by radiationfrom 3,290,788 Patented Dec. 13, 1966 an infra-red heating element, orby conduction heating from a heated shelf upon which the foamed andfrozen liquid is placed during the freeze drying operation. Durring thefoam and freeze portion of the cycle, Stratification occur-s and thedenser constituents of the liquid tend to settle in layers throughoutthe foamed, frozen and later dried block of liquid foodstuff. In asubsequent operation the freeze dried foam is milled and ground to adesired particle size. The resultant particles are not homogenous, cellsare ruptured in cellular type material such as tomato and as a result ofthese combined effects the dried particulate do not reconstitute readilyinto the original liquid material. In addition, this type of process isvery slow and costly.

In another method of freeze drying liquid materials the liquid issprayed onto chilled rollers and frozen into platelets, which aresubsequently passed'through a common infra-red radiation zone or driedon a heated shelf as described above. The dried platelets aresubsequently milled or ground to desired particle size. As in the foamfreeze drying technique some stratification and cell rupture stilloccurs with this process, as does some scorching of the product. Theresultant particles are not homogenous and do not readily reconstituteinto the original liquid.

It is also well known in the art to freeze liquid material into pelletsby spraying the liquid into a cold gas environment for the purpose ofobtaining a frozen particulated liquid to accommodate later processingin a freeze dryer or otherwise. While this type of frozen pellet ishomogenous, and there is somewhat less cell rupture, no water is removedduring the spray freezing operation. Furthermore, the remaining water isevenly distributed as ice-throughout the frozen particles interior andexterior. In addition the frozen particle is virtually non-porous. Whenthis type of frozen particle is processed through a freeze dryer ofeither the shelf or radiation heated type, the freeze drying operationrequires approximately the same length of time as for drying thepreviously described frozen platelets. The primary reason being that thedense, frozen particulate or platelet does not facilitate diffusion ofsublimed water vapor from the interior of the particle or plateletduring the later stages of drying when the freeze-front has receded intothe interior of the product. Furthermore, the heat for sublimationcannot be supplied at the highest intensity during the later stages offreeze drying because it would scorch or burn the already dried layer ofmaterial above the freeze front. As a result, the freeze drying ofeither frozen particles or platelets is much slower than the a methoddescribed in the present application. Also, the

freeze dried frozen pellets do not exhibit the required properties andcharacteristics which facilitate ready reconstitution into the originalliquid material. Rather, they tend to agglomerate or lump duringreconstitution.

Accordingly, a primary object of this invention is to provide a processand apparatus for low temperature desiccation of soluble, or primarilysoluble and insoluble organic materials in liquid solution which issusceptible to continuous operation. A related object is to provide amethod of initially freezing the liquid material into frozen particulatesolids and ice, while simultaneously removing some of the liquidscontained'water; and yet further to freeze the particulates in such amanner as to concentrate the remaining water, (ice) at or near the outerperiphery of the frozen particulate solid, while partially desiccatingthe particulates interior. A further object is to spray and freeze theliquid material so that pores, vents and cracks occur in the outerperiphery of the particulates to facilitate later water vapor removal.

. Another object is to freeze the liquid material instan- 3 taneously atvery low temperatures to effect transport of water from the interior ofcontained cells while forming the Water into ice in the intersticesbetween the cells, thereby avoiding cell rupture due to expansion offrozen water (ice) within the cells as occurs at slower freezing rates.Still another object is to provide an improved freeze-drying processwhich is capable of effecting the desired drying in a minimum amount oftime. Yet another object of the invention is to provide a freeze-dryingprocess which will produce extremely porous, discrete, amorphous orspherical particulate solids having a large surface area and a low bulkdensity, which are capable of being rehydrated without any loss offlavor and aroma. A still further object of the invention is to providea freeze-drying process wherein the radiant heat for sublimation isprovided at a specific wave length which will pass through most organicproducts, but not through ice; thereby permitting a maximum of intensityof heat for sublimation to be applied throughout the freeze-dryingoperation without danger of scorching or burning the organic materialand thereby facilitating speedier sublimation of the ice. A yet furtherobject of this invention is to provide means for accelerating watervapor removal from the particulate surfaces during the freezedryingoperation.

A feature of the present invention is to provide a method and meanswhereby soluble, or primarily soluble and insoluble organic materials inwater or other liquids are freed of the bulk of moisture or liquids inan early stage, and particulate matter surfaced with ice is recoveredsubstantially free of moisture or liquid in a later stage.

Another feature of the present invention is to provide a process asdefined in the preceding paragraph wherein a high velocity jet stream ofgas having a temperature below the freezing point of the organic liquidsolution is utilized to disintegrate the organic liquid solution into afine mist of moisture forming a very substantial portion of the liquid,and into particulate solids coated with ice. A related feature is toremove the moisture mists in the form of microcrystalline particles ofice at an early stage of the process, and to remove the frozenparticulate solids at a later stage of the process. A further relatedfeature of the present invention is to concentrate the organic materialand ice at or near the outer periphery of the frozen particulates and toremove the surrounding ice at a later stage in the process. A stillfurther feature of the present invention is to provide effective stepsand means for the removal of residual moisture in the particulatematter.

Still another feature of the invention is to provide processingapparatus and method steps for providing an economical super-cooledprocess gas, and recuperating said gas by substantially removing itscontained moisture while maintaining a super-cooled temperature tofacilitate reuse of the recuperated super-cooled gas in the process.

A still further feature of the invention is the provision of novel fluidbed apparatus including: a hollow vessel having heat transfer meansincluding a wall structure means within said vessel defining a pluralityof columns; grid means adjacent to the heat transfer means; means forintroducing a particulate substance int-o said vessel through an inletmeans; means for fluidizing said substance in said heat transfer means;means for heating said wall structure means; and means for removing saidsubstance from said vessel through an outlet means. A related object ofthe invention is to utilize a fluid bed apparatus described above in aprocess for desiccating organic materials.

Other objects, features and advantages will hereinafter become morefully apparent from the following description taken in connection withthe annexed drawing, wherein:

FIG. 1 is a schematic or flow diagram illustrating apparatus andprocedures steps embodying the invention;

FIG. 2 is a view similar to FIG. 1, but showing a first modified form ofapparatus and procedure;

FIG. 3 is a view similar to FIG. 1 and FIG. 2, but showing a stillfurther form of apparatus and procedure;

FIG. 4 is an enlarged, fragmentary, sectional view taken generallycentrally through the fluidized bed illustrated in FIG. 3;

FIG. 5 is a fragmentary side ture illustrated in FIG. 4;

FIG. 6 is a fragmentary enlarged sectional view taken centrally of thereaction vessel;

FIG. 7 is an enlarged central sectional through the liquid dispensingnozzle means;

FIG. 8 is an enlarged view taken generally along line 88 of FIG. 6; and

FIG. 9 is anenlarged sectional view taken generally along line 99 ofFIG. 8.

While this invention is susceptible of embodiment in many differentforms, there is shown in the drawings and will herein be described indetail only preferred embodiments, with the understanding that thepresent disclosure is to be considered as an exemplification of theprinciples of the invention and is not intended to limit the inventionto the embodiments illustrated. The scope of the invention will bepointed out in the appended claims.

The term gas is used in this disclosure to refer not only to inertgases, but also to air and mixtures of gas and air, and to otheraeriform bodies as well. The term super-cooled gas is used in thedisclosure to refer to any gas utilized at a temperature between itsliquid temperature and 32 F. References in the disclosure to an organicmaterial in liquid solution refer not only to primarily soluble organicmaterials in solution in water, but also to any primarily soluble andany primarily insoluble organic material in solution .in water and anyother liquid carrier such as alcohol, glycerine, petroleum, etc.

The methods and apparatus embodying the process have four distinctlydifferent operational stages which are illustrated in the drawings andcan be described in chronological sequence as: the liquid transport anddischarge stage; the liquid freeze-disintegration-evaporation stage; thefinal desiccation stage, which may be by gas ejectionsublimation, byvacuum radiation-sublimation, by fluidized bed evaporation, or bycombinations of each of these steps; and, a fourth stage embodying thegas supply and recuperation system.

STAGE ONE In stage one relating to liquid transport and discharge, theorganic-liquid solution which has first been expressed, extracted,pasteurized or otherwise prepared can be pumped, from a supply source,through a suitable pipeline to a desired level in the liquid surge tank.As illustrated in FIG. 1, the liquid is pumped through a solenoid valve2 and a suitable pipe-line 3 to the liquid surge tank 1 where thedesired liquid level is maintained by the liquid levelindicator-controller 4. Inert gas pressure is applied to the liquid inthe head space of the surge tank through a gas-line 5 which in turn issupplied from a suitable pressure regulated inert gas pressure vessel.Heating or cooling coils can be submerged in the liquid as required. Thepressurized organic-liquid solution is then discharged through asuitable control valve 6 and an insulated pipe-line 7 and a pressuredischarge nozzle 8 which is positioned within thefreeze-distintegration-evaporation vessel 9 of the second stage.Obviously, multiple discharge nozzles can be utilized to discharge theliquid solution from the surge tank into a largerfreeze-distintegration-evaporation vessel. In some instances gravityflow of the liquid solution will provide sufiicient pressure fordischarge. Such physical and chemical characteristics of theorganic-liquid solution as its percent solids content,

view of part of the structemperature and viscosity, will influence theliquids dispersion through the pressure discharge nozzle andsubsequently influence the size and bulk density of the discrete frozenparticulates formed during the freeze-disintegration-evaporationoperation.

The mechanism of dispersion of the liquid stream and its break-up byimpingement of the super-cooled inert gas jet streams is dependent onthe liquid streams discharge diameter and velocity, percent solidscontent, surface tension, and its viscosity. The principal object is toproduce a high ratio of surface to mass in the liquid phase bydispersing the bulk mass of liquid into turbulent filmy Waves expandingout from the nozzle orifice until the film sheets or ligaments can bereadily disintegrated and frozen by the super-cooled inert gas jetstreams to be hereinafter described.

The discharging liquid stream is turbulent throughout and is broken upby the impingement of the super-cooled inert gas stream. This can beexplained on the basis that the liquid stream is in turbulent flow andexhibits particle motion with radial velocity components, such that whenthe liquid stream is no longer confined by the discharge nozzlesorifice, the liquid film ligaments are restrained only by the surfacetension force of the organicliquid solution and dispersion of the liquidstream only occurs as the surface tension is overcome. The higher theviscosity of the liquid the longer will be the break up distance of thedischarged stream. When the pressure is increased, the liquid streamsbreak-up distance decreases.

The discharge nozzle is designed to facilitate liqui stream break-up byimparting tangential and axial velocity components. A design of pressurenozzle which appears to be most suitable features a discharge nozzlewhich has a circular orifice with a grooved venturi type throat whichwill emit the liquid product in the form of a turbulent hollow conehaving a cone angle of from 38 to 57. This type of nozzle induces fullydeveloped turbulence into the liquid stream before it issues from theorifice thereby inducing stability to the dimensions of the conicalturbulent dispersion it emits. This type of spray is readilydistintegrated by the impinging super-cooled gas jet streams within ashort distance from the discharge nozzle and within a small diametertube or vessel. The liquid stream which is emitted exhibits particulatemotion with strong axial and mild tangential velocity components. As aresult, the liquid, as it passes through the nozzle orifice forms aturbulent annular ring, or cone with an average velocity.

As the liquid is discharged into the vessel 9 a natural increase insurface will result followed instantly by expansion of individualdroplets due to the presence of higher pressure entrained gases in theirinterior which do not escape during the initial discharge through thepressure nozzle; and thereby sub-environmental pressures are createdwhich will cause voids or pores inside the frozen particulate.

STAGE TWO The freeze-distintegrationevaporation stage of the processcannot be treated as a unit operation It features three distinctlydifferent concurrent operational phenomena which can best be describedas the disintegration of the turbulent conically dispersed liquid streaminto water mists and droplets having; a nucleus of organic material, andthe simultaneous freezing of the resultant droplets into discrete frozenparticulates; the constant evaporation from the distintegrated dropletsand the simultaneous partial dehydration of the particulate nuclei; and,the flow of gases and motion of the frozen particulate solids within thevessel, and exhausting and discharging, from the vessel. A fourthfeature of the operation, the gas supply and recuperation system canalso accommodate the preceding and following stages of the process.

As the turbulent, dispersed stream of organic-liquid 6 concentrateenters the insulated freeze-disintegrationevaporation vessel 9, via theinsulated pipe-line 7 and discharge nozzle 8, it is disintegrated byimpingement of the high velocity, super-cooled inert gas jet streamsissuing from the gas nozzles and manifold 10 in counter-current flowwith respect to the flow of the organic liquid. Manifold 10 is suppliedfrom the gas supply and recuperation system to be hereinafter described.The angles of the impinging gas jet streams are such that they strikethe turbulent conically dispersed liquid stream tangentially in anupward sweep simultaneously freezing and disintegrating the turbulentconical liquid stream into an upward swirl of frozen particulate solidsand saturated cooled inert gas. The swirling saturated inert gas streamexits the vessel via the exhaust duct 11 which exhausts the gas to thegas recuperation and supply system. The resultant disintegration of saidfilmy liquid ligaments into an array of water mists and fine dropletsfurther enlarges the surface area of the bulk mass of organic-liquidsolution thereby facilitating the evaporation of the water mists and thefreezing of the larger organic-liquid drops to form discrete frozenparticulate solids. The water mists which are not immediately evaporatedexit the reaction vessel as micro-crystalline particles of ice.Evaporation of liquid from the surface of said frozen particulate solidsis caused by the friction created by the impingement of the super-cooledgas jet stream upon the solids. The interior of said frozen particulatesolids is partially dehydrated during their nucleation due to thecapillary attraction of the warmer liquid contained in the interior ofsaid particulates to their super-cooled surface, and thus a predominantpercentage of remaining moisture is concentrated in the form of ice atthe outer periphery of said frozen particulates. Growth of frozenparticulate nuclei by heterogenous and homogenous nucleation isfacilitated by entrainment of said nuclei by the swirling super-cooledgas jet stream, which circulate and recirculate said nuclei through thearea of the area of the aforementioned turbulent conically dispersedwavy liquid sheets or ligaments and their disintegrated array of mistsand droplets, thereby effecting condensate growth of organic-liquid uponthe outer periphery of said super-cooled nuclei until the mass of thefrozen particulate solid is sufficient to overcome the lift of theswirling supercooled gas jet streams, thereby permitting said frozenparticulate solids to gravitate through the orifice 12 in the conicalbottom of the vessel 9 into a quiescent zone 13 and through a rotaryproduct valve and discharge duct 14 which in turn is positioned withinthe third stage final desiccation vessel into which the said frozenparticulate solids are deposited.

The droplets created by disintegration of the organic liquid solutionare either pure Water, or water containing combined super-cooled solubleand/or insoluble/organic nuclei which will naturally be more hygroscopicand more thoroughly saturated with water. The combined soluble andinsoluble, hydrophobic, super-cooled organic I nuclei invariably consistof a non-hygroscopic insoluble super-cooled nuclei which lockshygroscopic soluble nuclei into the ice lattice of its surface forcefield. Such an aggregate therefore has a higher probability of attainingthe largest size as a frozen particulate solid.

Homogenous nucleation occurs as the super-cooled pure ice nucleuscollects small groups of water molecules which chance to. becomeoriented into an ice-like configuration on the super-cooled ice nucleus.The lower the temperature of the ice nucleus, the greater the size andfrequency of formation. At lower temperature there is a correspondingincrease in the rate of formation of pure ice frozen particulate solidsand their growth in size by homogenous nucleation of the water by thesupercooled pure ice nucleus.

The freezing of water containing combined soluble and/or insolublesuper-cooled organic nuclei which are either hygroscopic,non-hygroscopic and/ or combinations of both can be likened toheterogenous nucleation wherein the super-cooled organic nuclei initiatecrystallization and the formation of frozen particulate solids. Thetemperature required for heterogenous nucleation of the disintegratedliquid drops by super-cooled organic nuclei is considerably less tocreate a mean size of frozen particulate solid. Since heterogenous andhomogenous nucleation occur simultaneously, and at the same temperatureduring the freeze-disintegration operation; and the rate of formationand growth of frozen particulate solids of pure ice (homogenousnucleation), is slower than the formation and growth particulate solidswith organic nuclei (heterogenous nucleation), at a given temperatureand in a given time; it follows that the primarily organic particulatesolids formed are substantially larger and more numerous (about 90-95%)than the pure ice particulates.

The growth rate of the particle is controlled not only by the rate atwhich water vapor diffuses to its surface, but by the rate ofcondensation, which is limited by the rate at which the liberated heatof evaporation is dissipated. Nearly all this heat is lost from theparticulate surface by convection through the swirling gas stream.

Fundamental to the liquid disintegration and freezing operation are thesimultaneous heat and mass transfer processes occurring during theevaporation of the water mists and the evaporation from the droplets inthe spray. The evaporation from droplets will consist of a period ofsurf-ace evaporation, or constant-rate evaporation period, followed by aperiod when the evaporation rate falls off continually, or thefalling-rate period. During freeze-disintegration of the liquid streamthe constant rate period and the falling-rate period occursimultaneously and in a matter of seconds. The rate of heat transferfrom drops to the surrounding gas medium will be proportional to thedroplet surface area; the thermal conductivity of the surrounding mediumand the temperature difference. Dissolved organic materials will lowerthe normal vapor pressure of the liquid and the vapor pressure andtemperature differences causing mass and heat transfer, respectively,are lowered so that the evaporation rate will be less than for the purewater drops.

In addition to the effect on the vapor pressure the presence of solidsintroduces all the complications usually encountered in the falling-rateperiod of the drying of solids. For the evaporation of drops containinga dissolved component the drop evaporates as though it were saturatedeven though its average concentration is well below saturation. This canbe explained on the basis that the rate of diffusion of the dissolvedmaterial back into the drop is slow compared with the evaporation rate,and hence the solids concentrate at the surface of evaporation fasterthan they can diffuse toward the center of the drop. Pure liquidcontained within the interior is also drawn to the cooled surface of thedrop or particulate by capillary action, also facilitating the transferof heat to the surface of evaporation.

It can readily be seen from the preceding, that the liquid dropletswhich contain organic materials will be transformed into discrete frozenparticulate solids whose interior will be partially desiccated and veryporous and whose outer periphery will consist of primarily solubleand/or insoluble organic material which has served as the nucleus forcontinuous condensation-evaporation-com densation until the condensatelayer has increased the particulate mass to the point where it canovercome the velocity of the gas stream and fall to the discharge tubeof the vessel.

In addition to supplying the energy for disintegration and freezing thegas flow aids in dispersing and mixing the liquid stream. The frozenparticulate solids also tend to follow the gas flow pattern. In thearrangement depicted in FIG. 1, the gas jet stream enters tangentiallyupwards, creating a spiral with tangential velocities of 10 to times themagnitude of the axial velocity, thereby facilitating both particlemotion and gas exhaust.

The high initial velocity of the liquid stream causes it to penetratesome distance into the tangentially upward impinging gas jet streamsbefore disintegration-freezing, and deceleration of the terminalvelocities. As the disintegrated liquid droplets and /or frozenparticulates lose their initial momentum, they begin to follow thespiral motion of the gas stream. The particle falling at its terminalvelocity is subjected to the drag of the centrif-ugal field andgradually takes on radial and tangential components. Its resultantvelocity is due to the combined effects of gas friction in a tangentialdirection, centrifugal force, gravity, and the axial component of gasstream flow.

With the super-cooled gas stream issuing through several nozzles at anangle to the radius and between 25 and 35 to the circumference of thevessel the gas spiral is slightly less than the diameter of the vesseland diminishes in diameter as the angle of the circumference increases.

If the velocity of the counter-current flow of gas is sufficient thefrozen particles will turn to the area of the liquid streamdisintegration again and again (resulting in the nucleation phenomenapreviously described) until finally their mass will overcome thevelocity of the gas stream and they will gravitate to the rotary productvalve and discharge duct which facilitates transfer of the frozenparticulate solids to the final desiccation vessel.

The frozen organic particulate solids discharged from the liquidfreeze-disintegrationevaporation operation are discrete frozenparticulate solids with a partially dehydrated and very porous interiorand a roughly spherical, or amorphous outer periphery. This outerperiphery consists of a somewhat denser, yet porous, shell of organicmaterial which has served as the super-cooled nucleus for thecondensation growth'and, simultaneously, as the surface of evaporationduring the growth of the condensed ice layers.

The water which has not been evaporated in the operation is predominantas ice at the surface of the frozen particulate solid where it can beremoved readily in the final desiccation operation, either byejection-sublimation, vacuum-radiation sublimation, or fluidized bedevaporation; or a combination of each as will be shown hereinafter.

Manifestly, the higher the pressure of the inert gas, the more thoroughwill be the disintegration of the organic liquid. While gas pressures inthe range of 2000 p.s.i.a. have been found to be most desirable,pressures of 45 p.s.i.a. to p.s.i.a. have proved to be effective. It ispreferred that there be a temperature difference of at least 2000" F.between the inert gas and the liquid product, however, temperaturedifferences approaching 400 F. are most desirable. It is also preferredthat the inert gas enter the reaction zone at a high velocity, as, forexample, in the range of 6-50 feet/ sec.

Referring now to FIGS. 6-9, where-in a preferred form of Stage Twoapparatus is shown, it will be noted that the wall of the reactionvessel 9 is relatively thick, and it will be understood that thereaction vessel is formed of a suitable insulating material. The liquidinlet pipe 7 extends into the vessel through an opening in the sidethereof, and is surrounded by a tubular jacket 101 which extends fromside to side of the vessel to support the nozzle assembly therein. Anelbow 102 connects pipe 7 with a downwardly extending pipe 104; and a T-connection 103 connects the tubular jacket 101 with a downwardlyextending tubular jacket member 105, which is positioned in spacedrelationship with respect to pipe 104. Insulating packing, or the like,is provided in the tubular passages between pipe 7 and jacket 101, andpipe 104 and jacket 105 to retain the liquid flowing through pipes 7 and104 at a constant temperature. Nozzle 8 is a conventional commerciallyavailable variety, which is adapted to disperse the liquid into thereaction vessel in the aforementioned conical spray (as is showngeneral- 9 ly at 107 in FIGS. 7 and 8), and includes a circular orifice108 and a grooved throat 109. Nozzle 8 extends downwardly through anopening in an end cap 106 which is fixed on the lower end of jacketmember 105.

Manifold 10 is generally circular in plan view and is positioned in thereaction vessel below nozzle 8 and concentric therewith. An annular ring111 supports the manifold 10, which in the illustrated form is definedby the arcuate ends of inert gas inlet pipes and 15. A plurality ofnozzles 112 are positioned around manifold 10, and each includes anupper nozzle member 113 and a lower nozzle member 114. As can be bestseen in FIG. 9, each of nozzle members 113 and 114 is directed upwardlytoward spray 107, and as can be best seen in FIG. 8, the gas flowingfrom nozzle members 113 and 114 is directed generally tangentially tothe spray 107. Thus, the resulting micro-crystalline particles of iceescape from the reaction zone and pass upwardly, as indicated bydirectional arrows 115 in FIG. '6, to the exhaust duct 11 along with thesaturated exhaust gas. The frozen particulate solids follow a pathgenerally indicated by directional arrows 116 in FIG. 6, wherein theypass outwardly from the reaction zone toward the wall of the vessel, andthen are drawn upwardly back into the reaction zone by the suction ofthe gas issuing from nozzles 112. Nucleation and particle growth of thefrozen particulates occur as they reenter the reaction zone, until theyare a sutficient mass to overcome the force of the incoming gas, atwhich time they will fall into the quiescent zone 13 at the lowerportion of the vessel.

GAS SUPPLY AND RECUPERATION As previously mentioned, the high velocity,supercooled, nitrogen gas is issued from the gas jet nozzles 10. Theliquid nitrogen gas is stored in the storage dewar 18, at a temperature(for nitrogen) of (320 F.). The liquid nitrogen supply can be maintainedby a cryostat 19 which uses either atmosphere or nitrogen gas from thepressurized nitrogen gas storage vessel for liquefaction. Thesuper-cooled gas boil-off from the liquid nitrogen contained in thestorage dewar is issued through the gas line 15 and regulating valve 16and mixed with warmer nitrogen gas issuing from the condenser 22 and thecentrifugal compressor 21, through the gas-line and regulating valve 17.The flow and mixture ratio of warm and supercooled gases issuing throughthe regulating valves 16 and 17 is controlled by the temperatureindicator-controller 17 whose thermocouple is located in the gas-line15. The mixed gas is issued through the gas-line 15 to the gas jetmanifold and nozzles 10 which is positioned within the vessel 9. Drynitrogen make-up gas can be issued, as required, from the storage vessel20 through the gasline to the regulating valve 17 and mixed with thecool gas exhausted from the condenser 22 by the compressor 21.

The saturated'nitrogen exhaust gas exits the vessel via the exhaust duct11 and is ducted to the plate-type condenser 22 and then to thecentrifugal compressor 21 where it is compressed and charged intogas-line and valve 17 to be mixed with the gas issued from the gasline15, etc., etc. Super-cooled nitrogen gas is also supplied to thecondenser 22 through the gas-line and valve 23 and subsequentlydischarged through the gas-line and valve 24 and ejected into thegas-line 15, etc., etc.

The nitrogen gas suppl and recuperation system can also accommodate thefirst and third stages of the process. The pressurized nitrogen gas fromthe nitrogen gas storage vessel can supply the required inert gaspressure (via the gas-line and pressure regulating valve 5) to thepressure head of the first stage liquid transport and dischargeoperation, and, as will be shown hereinafter, the system can alsoaccommodate the third stage final desiccation system via the gaslinesand valve 26, 27 and 28.

STAGE THREE The final desiccation of the discrete frozen particulatesolids is accomplished by the apparatus and steps embodying the thirdstage of the process. A variety of apparatus and steps can be utilizedfor the third stage. All of these variations fall into one of fivegeneral categories of final desiccation methods which can be describedas: final desiccation by forced gas (or air), ejection-sublimation;

- final desiccation by vacuum-radiation sublimation; combined partialdesiccation by forced gas (or air), ejectionsublimation followed byfinal desiccation in a vacuumradiation sublimation apparatus; finaldesiccation by fluidized bed evaporation; or combined partialdesiccation by fluidized bed evaporation followed by final desiccationin a vacuum-radiation sublimation apparatus.

Such physical and chemical characteristics of the frozen particulatesolid as the percent ice content within it, and/or upon its outerperiphery, its resistance or adaptability to various final desiccatingtemperatures, environments and processing steps, and its quality controlrequirements determine the selection of the particular final desiccationmethod which is utilized to effect the desired end productcharacteristics.

FIG. 1 illustrates the apparatus and technique embodying the forcednitrogen gas ejection-sublimation method of final desiccation whereinrecuperated, recycled nitrogen gas and compressed make-up, nitrogen gasare used to effect the final desiccation.

The frozen particulate solids formed in the second stagefreeze-disintegration-evaporation vessel 9 are super cooled and featurea predominance of their remaining moisture content in the form of ice attheir outer surface, subsequently the particulates remain substantiallyseparated as they are transferred via the insulated rotary product valveand discharge duct 14 which is attached to the ejection chamber 35,wherein they are entrained by high velocity, low temperature nitrogengas expanding from the divergent ejector nozzle 32, which is positionedwithin the ejection chamber 35. The propelling high velocity lowtemperature gas expanding from the ejector nozzle 32 is converting itspressure energy into velocity energy. This mass of gas is dischargedfrom the nozzle 32 in a directed flow through the ejection chamber 35and into a convergent-divergent diffuser 36.

As the gas stream passes through the ejection chamber 35 it comes incontact with, and entrains the definite mass of super-cooled frozenparticulate solids and some gas which has been discharged from theproduct valve and duct 14. It imparts to this mass a portion of its ownvelocity by being decelerated, and most of its heat energy by exchangewith the super-cooled particulate mass, effecting sublimation of the iceon the particles outer periphery, and the release of water vapor whichthen is also entrained. The resultant combined total mass, at theresultant velocity enters the diffuser section 36 where its velocityenergy is, in greater part, again converted into pressure (and heatenergy), thereby effecting further sublimation of the entrainedparticles surface ice. The higher pressures attained permit theresultant combined total mass to be discharged to the higher pressure(than in the ejection chamber 35) cyclone dryer chamber 37.

As the combined total mass (particles-water vaporpropelling gas) isexpanded from the divergent diffuser section 36 it is impinged by amoderate velocity, dry nitrogen gas which is simultaneously expandingfrom the divergent ejector nozzle 34, positioned at a right angle to it.The resultant turbulent dispersion of the combined total mass of the twostreams is decelerated and exchanging heat, thereby effecting furthersublimation. This resultant combined total mass, at the resultantvelocity enters the convergent lower portion of the cyclone dryerchamber and is discharged into the quiescent conical exhauster-separatorzone 38, wherein the dried, or substantially dried particles precipitateto the lower portion and are removed via a rotary product valve anddischarge 1 l duct 39. The water vapor-gas stream and any entrained,fine product dust, are exhausted via the exhaust duct 40 by thecentrifugal blower 48.

The substantially dried particulate solids discharged through the rotaryproduct valve and duct 39, into the supplementary ejection chamber 41,are entrained by a high-velocity dry nitrogen gas stream expanding froma divergent ejector nozzle 42, compressed through theconvergent-divergent diffuser section 43 and discharged tan-. gentiallyinto the supplementary cyclone-dryer 44, the desiccated particulatesolids precipitate to the conical lower quiescent zone 45 and areremoved via the rotary product valve and discharge duct 46. The combinedwater vapor-gas stream and any entrained, fine, product dust, areexhausted via the exhaust duct 47 by the centrifugal blower 48. Thesupplementary or second stage, desiccation components 41 to 47 are onlyrequired for final desiccation of certain products.

The combined water vapor-gas and dust stream are exhausted via theexhaust ducts 40 and 47 by the centrifugal blower 48 through thecombined exhaust duct 49, to the optional, dual, alternating,electrostatic precipitators 50, wherein all remaining entrained productdusts are collected (when required). The combined water-vaporgas streamis issued from the electrostatic precipitator, through its exhaust ducts51 to the dual, alternating, plate type condensers 52 whose plates arerefrigerated by supercooled nitrogen gas issued through the insulatedgas-line 26 and exhausted via the insulated gas-line 28 through which itis returned to the nitrogen gas supply and recuperation system aspreviously described. Condensate is periodically removed from thecondenser plates by alternately cycled heated air issued through thesame gasline 26.

The water vapor saturated, gas stream is drawn through the platecondenser by the multi-stage axial flow compressor 53 which, in turn,compresses the cooled and dried gas (which subsequently gains heatenergy) and re-ejects it through the divergent ejector nozzle 32 whichis positioned within the ejection chamber 35. High velocity, drynitrogen make-up, gas can be added, as required, via the gas-line anddivergent ejector nozzle 31 which is supplied from the pressurizednitrogen gas storage vessel 20 via the gas-line 27 through the auxiliarygas heater 29 which is equipped with an interlocked temperaturecontroller-indicator 30, and the gas-line and regulating valve 33, whichalso issues heated nitrogen gas to the ejector nozzles 31, 34 and 41.

FIRST ALTERNATE STAGE THREE FIG. 2 illustrates an alternate finaldesiccation apparatus and process wherein compressed air is employedtogether with super-cooled nitrogen for the freeze-disintegration andevaporation of the starting material and wherein the frozen particulatesolids are substantially dried and then transferred to a finaldesiccation apparatus which employs a vacuum radiation sublimationapparatus to effect the final desiccation. In the operation of theapparatus shown in FIG. 2, the liquid starting material is dischargedfrom the pressurized vessel 1a into thefreeze-disintegration-evaporation vessel a, which is substantially thesame as vessel 9 heretofore described.

Instead of supplying a single gas such as nitrogen to vessel 9a, thenitrogen is combined with compressed dry air in such proportions as togive the desired gas temperature and velocity in vessel 9a. For example,nitrogen from the storage vessel 18a may be combined with compressed airfrom the storage vessel 20a, as indicated by the flow lines, and thecombined material, after passing through a condensate trap, isintroduced through line 15a into the manifold 10a of vessel 9a. Thesuper-cooled gas jets 10a in vessel 9a serve to disintegrate the chargedliquid as heretofore described in connection with vessel 9, and thesaturated gas and air medium is withdrawn through exhaust duct 11a whilethe frozen solid material is recovered through the valve-controlledoutlet 14a.

High velocity dry compressed air is introduced through line 27a andafter passing through an auxiliary air heater 29a, is discharged intothe ejection vessel 35a which operates substantially as the vessel 35described in connection with FIG. 1. The vessel 35a dischargestangentially into the cyclone vessel 37a and the turbulence of thematerial is increased by introducing nitrogen gas or other inert gasthrough nozzle 34a at high velocity. The vessel 37a is substantially thesame as vessel 37 heretofore described. The organic particulates solidsare collected in quiescent zone 38a and discharged therefrom via valveand duct 39a. Gas bearing particulate matter is withdrawn throughexhaust duct 40a and delivered to the cyclone-separator 4411/ Gasbearing particulate matter passing through precipitators 50a is removedthrough the blower-operated exhaust 48a, the solids being collectedwithin the quiescent zone 45a are discharged through valve and dischargeduct 46a to the receptacle 54.

The particulate solids received within the receptacle 54 are dischargedthrough alternating air locks 55 and 56 onto a continuous belt conveyor57 within a vacuum ves sel 58. It should be pointed out that as onealternate processing method the rotary product valve and discharge duct14a of the second stage may be connected directly to the vacuum vessel58, and for certain products the forced gas, ejection-sublimationapparatus and steps described above may be omitted. The frozen particleson the belt conveyor 57 are exposed within the vacuum environment to aselected wavelength radiator 59 which emits approximately of itsradiation between 0.9 micron wavelength (9,000 A. units) and 1.3 micronswavelength (13,000 A. units). This wavelength radiation readilypenetrates planten and albumin tissues in depth (up to 1000 micronsdiameter and more preferably 650 microns), so that heat is provided toeffect the sublimation of the ice surrounding the organic materialwithout causing any heating of the material itself. Therefore, a maximumsupply of heat for sublimation of ice is radiated to the frozenparticulate solids, thereby accelerating the sublimation action Withoutdanger of scorching the outer periphery of the particles. Means, notshown, are preferably provided to intermittently drive conveyor 57 sothat the particles will be periodically tumbled and periodically exposenew surfaces to the radiation source.

Albumin tissue for example can be penetrated by 90% of radiation between0.9 micron and 1.25 microns (75% at 0.9 micron wavelength, at 1.2microns wavelength) and absorbs all radiation over 1.3 micronswavelength at its surface-planten tissue can be penetrated by radiationbetween 0.85 micron to 2.9 microns wavelength.

During the sublimation operation, the frozen particulates which are tobe dried are simultaneously subjected to radiant energy in the selectedwavelength, which is issuing heat, relative to the ice, evenlythroughout the product (i.e., no excessive heating of the productssurface by absorbed wavelength radiation over 1.3 microns wave lengthand/ or under 0.9 micron wavelength), and maintained under a vacuumpressure gradient which keeps the product in the solid or frozen statewhile the moisture therein is converted to vapor and transported to thesteam-ejector evacuation system.

By supplying the heat of sublimation in the selected wavelength (0.9 to1.3 microns wavelength) the material is heated substantially uniformlyin depth, and there is no scorching of the outer periphery of theproduct because it receives a minimum (less than 5%) of non-penetratingradiation (over 1.3 microns wavelength and/ or under 0.9 micronwavelength) and is also cooled by the escaping water vapor throughoutthe drying period.

The parameters which control the transfer of heat to the material arethe conductivities, emissivities, specific heats, and radiationabsorption coefficients of the appa ratus components, the material andthe driver gas.

This selected wavelength of radiation can be achieved with variety ofcomponents, selection of which is determined by the net flow of heatenergy (between 0.9 and 1.3 microns wavelength) required. The simplestarrangement is to use: (1) any convenient infra-red radiation sourcesuch as tungsten or nickel-chromium wires operating at a temperature of2500 K., which transmits 70% of its total radiation in the spectralrange between 0.8 and 8.9 microns wavelength with maximum intensity at2.3 microns; (2) any convenient filter source which will pass a maximumof radiation between 0.9 and 1.3 microns, lead glass will transmit 90%of radiation in the 1.0 to 3.0 micron range (with maximum transmissionat 1.0 microns) and will filter out 70% of all radiation above and belowthis wavelength. A A" thick water filter will transmit 90% of radiationbetween 0.9 to 1.3 microns (90% at 0.9 micron, 100% at 1.0 microns, 55%at 1.2 microns, at 1.3 microns and nothing over 1.7 microns). A selectedwavelength radiator utilizing the most desirable arrangement ofinfra-red source and filter-s will transmit 90% of its radiant energybetween 0.9-1.3 microns wavelength. A wide variety of energy sources,reflectors, filters and simple gratings can be utilized to effect theselected wavelength required for penetrating a given material in depth.

The sublimed water vapor is removed through the evacuation manifold 60preferably by a four-stage steamejector evacuation system (not shown) ofadequate capacity for removing the sublimed water vapor whilemaintaining the required vacuum pressure (approximately 1 mm. Hg). Thesteam-ejector evacuation system will also provide sufiicient pumpingspeed to permit the bleed-in of inert gas issued through line 61, whichcan provide supplementary heat for sublimation, directly to the icedouter periphery of the frozen particulate solids while simultaneouslyproviding a driving force to accelerate water vapor transport to theevacuation system. The driver gas stream issued through line 61 isdirected across the particles surfaces during sublimation, therebyeffecting a pressure gradient between the particles surfaces and theenvironment, to provide means for driving the water vapor moleculesescaping from the particles surfaces along the pressure gradient and ina directed stream toward the evacuation manifold 60. Thus, the drivergas reduces the incidence of water vapor molecules returning to theparticulate surface during sublima' tion, and the rate of rem-oval ofwater vapor from the particle surfaces and the vacuum vessel isincreased.

The desiccated particulate solids drop off the conveyor belt 57 and fallinto a collector trough 62, from which they precipitate to the dualalternating interlocked discharge air locks 63 and 64, the final productbeing discharged through outlet 65.

j The mechanism of vacuum-radiation sublimation can be postulated to bea combined heat-mass transfer principle of operation, wherein theselected wavelength radiator supplies the penetrating heat forsublimation to the ice crystals in a vacuum environment, thereby causingthe Water molecules to sublime from the free surfaces of these crystals.After a water molecule sublimes it passes into the vacuum environmentwhere, after an indeterminate number of collisions with other escapingWater vapor molecules and collisions with the vacuum chamber walls andthe bleedin driver gas, it eventually reaches the evacuation systemwhere it is permanently removed from the system.

A net flow of water vapor between the ice crystal and the evacuationsystem requires the establishment of a pressure gradient. Thus, forthere to be a net flow, the average concentration and so the pressure inthe vacuum environment is less than the pressure of the water vapormolecules escaping from the ice crystal. The driver gas, i.e., a highvelocity, dry super-cooled gas stream directed across the ice surfaceand to the duct of the evacuation system, but having a net pressure atthe ice crystal less than the saturated vapor pressure over ice at thetemperature of the ice surface, but :high enough pressure and velocityto drive the escaping water vapor molecule from the surface of the icecrystal to the evacuation duct, thereby driving the escaping andcolliding water vapor molecules in a direct path to the evacuation ductrather than permitting them to follow a random path.

As drying proceeds, sublimation takes place only from the surface of theice. As the ice surface recedes within the product, the heat ofsublimation must ordinarily be transferred in from the outer surface.According to the particular arrangement used, the heat may flow througheither a layer of frozen materials or a layer of dried material. It isdesirable to keep the surface at a constant temperature as long as anyice phase remains. If heat is being transferred through a layer offrozen product, the surface temperature must be kept below the freezingpoint. If drying takes place from the heated surface, heat must flowthrough a layer of dried material. Because of the low thermalconductivity of the porous, dry material, the surface temperature islimited by the thermal sensitivity of the dry solid rather than bymelting of me.

Most liquid and all solid food products are sufliciently opaque thatmost heat radiation will not penetrate to any significant distance.Since drying takes place from all surfaces of the product, it isdifiicult to maintain the optimum rate of heat input without scorchingthe dry surface. In the present vacuum-radiation sublimation processthis difficulty is overcome by utilizing the selected wavelengthradiator described above.

SECOND ALTERNATE STAGE THREE Figure Three illustrates the apparatus andtechnique embodying the fluidized bed evaporation method of finaldesiccation, wherein exhaust gas issuing from Stage Two is recuperatedand recycled, together with dry make-up gas or air and used to effectthe final desiccation.

The term fluidization is used to designate the fluid-solid contactingprocess in which a bed of finely divided solid particles is lifted andagitated by a rising stream of process gas. At sufficiently high fluidvelocity, the particulate bed will be lifted. Since the particles arenot bonded together they will move farther apart and open up theinterstices to allow easy passages of the gas fluid, and thus the bulkdensity decreases and the bed expands in volume. At velocities greatenough to give a pressure drop equal to the weight of the material inthe bed per unit area of columncross-section, the bed expands so thatall the particles are no longer touching, and the bed is in the fluidstate.

Certain of the apparatus used in conjunction with the fluidized bedevaporation apparatus is the same as that described above, and commonreference numerals have been used, with the subscript b having beenadded to designate the parts in the fluidized bed evaporation apparatus.

As has been explained above, the turbulent dispersed stream of organicliquid concentrate enters the insulated reaction vessel 9b from thepressurized liquid storage vessel 1b, via the insulated pipeline 7b anddischarge nozzle 8b, where it is disintegrated by impingement of thehigh velocity super-cooled gas jet stream issuing from the ring manifold10b, which in turn is supplied by the insu'.

lated pipeline 1512 leading from the gas supply system. The swirlingsaturated gas stream exits the vessel via the exhaust duct 1112 whichexhausts the gas to the gas recuperation system. The frozen particulatesolids exit the vessel through rotary product valve and discharge duct14b, which is inserted in the ejector chamber section of theconvergent-divergent.manifold 35b. The particulates are entrained byhigh velocity cold gas expanding from the divergent ejector nozzle 32bthat is positioned within the ejector chamber of theconvergent-divergent manifold A rotary impact screen chamber 70 ispositioned in exhaust duct 11b, and is provided with several fine meshrotating screens which trap the ice particles in the saturated exhaustgas. As the screens are rotated, the ice is melted and drained out ofthe chamber. The ice-free saturated exhaust gas leaving the impactscreens passes through an optically tight cryogenic trap 71 wherein thewater vapor entrained in the exhaust gas is condensed on liquid nitrogencooled baflles, which in turn are supplied with liquid nitrogen from apressurized storage dewar 66, through regulating valve 68, and lines 67and 71a. The subsequent boil-off of vaporized liquid nitrogen iswithdrawn via line 71b and returned to the gas supply system, wherein itis mixed with compressed air after passage through a heat exchanger 72,and transported via pipeline 15b to the gas jet manifold b.

When saturated gas is cooled Well below its dew point, it is possible tocondense substantially all of the water vapor and dry the gas. Thesaturation of the gas leaving the cryogenic trap 71 will be nominalbecause its dew point approaches the surface temperature of thesuper-cooled baflle plates as a result of the heat and mass transferthat occur at the boundary between the gas and the cooling plates.Condensate is periodically removed from the cooling plates of thecryogenic trap, either by issuing heated air through the plates, or bycirculating heated air or stream through the condenser. While thecondensate is evaporatedin one condenser, the saturated gas stream canbe exhausted into an alternate dual condenser (not shown), and viceversa.

The essentially dry (and colder) exhaust gas exits the cryogenic trap 71via line '73, and is issued into a heat exchanger 74 wherein it is mixedwith dry make-up gas or compressed air, as required. The combined coldgas stream leaves the heat exchanger 74 via line 74a and is finallyexpanded from the divergent ejector nozzle 32b, which is positionedwithin the ejector chamber section of the convergent-divergent manifold35b.

The propelling high velocity cold gas jet stream expanding from theejector nozzle 32b is converting its pressure energy into velocityenergy. As this mass of cold dry gas is discharged in a directed flowthrough the ejector chamber it comes in contact with, and entrains thedefinite mass of super-cooled frozen particulate solids, which areissued from vessel 9b via duct 14b into the ejector chamber. The gasimparts to this mass a portion of its own velocity by being decelerated,and most of its energy by exchange with the super-cooled particulatemass, effecting some evaporation of the ice on the particles outersurface, and the release of water vapor which then is also entrainedwith the gas flow. The resultant combined total mass enters theconvergent-divergent section of the manifold 35!) where its velocityenergy is, in greater part, again converted into pressure (and heatenergy), thereby effecting further evaporation of the entrainedparticles surface ice. The higher pressures attained permit theresultant total mass to be discharged via the divergent entrance to afluidized bed reaction vessel 75, through a grid 76 at the lower portionof vessel 75, and into a resistance heated multiple honeycomb columnstructure 77 spaced vertically above grid 76. The combined cold gas andparticle stream becomes decelerated and fluidized in the honeycombcolumn structure 77, and exchanges heat with the heated walls of thehoneycomb column structure to effect further evaporation andintermediate final desiccation of the frozen particulate solids. Thehoneycomb column walls are formed of extremely thin stainless steeland-are resistance heated by a low voltage-high ampere current suppliedby a D.C. rectifier 78. Column wall temperatures of from 250 F. to 450F. have functioned satisfactorily to dry the particulates withoutscorching. Grid 76 is also preferably formed of stainless steel.

As the frozen particulate solids whose remaining water content ispredominant at the outer periphery in the form of ice are fluidized, thefinely divided particulates are lifted and violently agitated by therising stream of cold process gas. At a sufficiently high velocity theparticulate beds will be lifted above the grid 76 into the individualheated honeycomb columns 77. Since the particles are not bonded togetherthey will move further apart, opening up the interstices to allow easypassage of the gas fluid. Thus, the bulk density decreases and the bedexpands in volume within each individual honeycomb column. At velocitiesgreat enough to give a pressure drop equal to the weight of the materialin the bed per unit of column cross-section, the bed expands so that allthe partioulates are no longer touching, and the bed is in the fluidstate. The volently agitated frozen particulates are constantlycirculating and contacting the heated honeycomb walls effecting rapidevaporation from the ice surface. Because of the violent agitation ofthe particles, different portions of the particles are intermittentlycontacting the heated columnar structure, and thus the rate of heattransfer to the particles will be uniform. Simultaneously the coldprocess gas is warmed up as it passes through the heated column Wallsand through the interstices between particulates, thereby enabling thegas to carry a greater proportion of water vapor before becomingsaturated. At no time does the process gas exceed 32 F. Even though thefrozen particulates come into momentary contact with the heated columnwall, they also never exceed this temperature. As a result of theintermittent momentary contact with the heated walls, evaporation fromthe particulates ice surface remains at the highest or constant ratedrying period.

As the ice surface of the frozen particulates is evaporated, they haveless bulk density and become airborne, so that they flow upwardly invessel 75 and are removed with the saturated exhaust gas via the cyclone79, which communicates with the upper portion of vessel 75. Cyclone 79functions to separate the particulates from the gas, with the gasflowing upwardly out of cyclone 79 to exhaust manifold 94, and theparticulates pasing outwardly from the bottom of cyclone 79. Thesubstantially desiccated particulates may then be reprocessed through asimilar second or third stage fluidized bed for further desiccation, orto an alternate final desiccation apparatus which features continuousvaccum-radiation sublimation and is described hereinafter. When furtherdesiccation is to be accomplished by the use of one or more additionalfluidized beds, the gas exhausting from manifold M is preferably heatedto increase in moisture carrying capacity and reused in the next stagefluidized bed. To effect this, the gas may be passed through a dryer 95and heater 96 (FIG. 3), or alternatively, warm make up gas may be addedto the gas exhausting from manifold 94, if desired. In a preferredprocess, the gas exhausting from the first stage fluidized bed is heated27 F. from 32 F. to 59 F. to substantially double its moisture carryingcapacity prior to its use in the second stage fluidized bed. The gasexhausting from the second stage fluidized bedis heated to 86 F. andreused in a third stage fluidized bed,

and it has been found that in many cases and for many products the threestep fluidized bed will achieve the desired degree of product dryness.

As can be best seen in FIG. 5, the fluidized bed 75 is preferablymounted upon a support 80 having an up wardly facing arcuate recess 81.The lower end 82 of fluidized bed 75 is rounded, so as to be shapedcomplementarily to recess 81 whereby the fluidized bed 75 is capable ofbeing inclined on the support 80 without difficulty. Any suitable meansmay be provided to incline the fluidized bed 75, and as may be best seenin FIG. 5, the fluidized bed is capable of being inclined through arelatively wide angular range, as shown by the broken line position at75a. It will be readily appreciated that when the fluidized bed isinclined with respect to the path of the incoming gas entrainedparticulate matter, the incidence of collisions between the particulatesand the sides of the honeycomb 'c-olumns will be increased. Thus, bymerely inclining the fluidized bed 75, the rate of evaporation from theparticulates can be increased, and the rate of evaporation can be variedand controlled by changing the angular inclination of the bed 75. Theoperation can also be controlled by maintaining the exhaust gastemperature constant, by adjusting the inlet gas temperature, and byadjusting the column Wall temperature to meet varying demands on thesystem. One of the major advantages of the fluidized bed multiple columnstructure is that the ratio of column diameter to bed height can bemaintained for optimum fluidization, while maintaining a low vesselheight. That is, the diameter of the bed may be doubled or tripledwithout increasing the bed height, so long as the interior column heightto diameter ratio is maintained. This arrangement also facilitates theequal distribution of heat for evaporation by heating all of the columnsequally. It will also be appreciated that the multiple column structurealso provides greater surface area for distributing heat to thefluidized particles.

The desiccation apparatus and process illustrated in FIG. 3 may alsoinclude a vacuum-radiation sublimation method of final desiccation,similar to that previously described. When a final desiccation step isnecessary or desirable, the partially desiccated particulates passingfrom the fluidized bed evaporation vessel are transferred from thecyclone 79 into a receptacle 54b, and thence to a pair of alternatingair locks 55b and 56b. The particulates precipitate alternately throughdual interlocked and alternating vacuum gate valves 81 and 82 into theloading or entry air locks 55b and 56b, respectively. Air locks 55b and56b are then evacuated via the dual evacuation lines 83 which areequipped with dual, interlocked alternating vacuum valves 84 and 85,which communicate with the evacuation manifold 86 that exhausts into theevacuation system shown generally at 87. When the entry air locks 55band 56b have been evacuated to the pressure of the vacuum vessel 5812,the dual interlocked alternating exit vacuum gate valves 88 and 8 9 areopened, permitting the particulate solids to precipitate into the vacuumvessel 58b. A manually operable agitator 90 may be provided in duct 91to evenly spread the particulates to a desired depth on a suitablecontinuously moving conveyor belt 57b. It should also be understood thata rotary discharge spreader may be substituted for the manually operableagitator, if desired. The evenly spread layer of particulate solids,which have a substantially dehydrated interior and have their remainingwater content in the form of ice substantially situated at their outerperiphery, are conveyed under the selected Wavelength radiator whichemits 90% of its radiation between 0.9 micron wavelength (9,000 A.) and1.3 microns wavelength (13,000 A). A radiation shield 92 is preferablyprovided above radiation source 5% in vessel 58b to reflect the raysdownwardly onto the product on belt 57b. Means may be provided foragitating belt 57b so as to constantly turn the particulates over andpresent new surfaces for receiving the radiant heat.

The sublimed water vapor is remove-d through the evacuation manifold 60bby a four-stage steam ejector evacuation system (not shown) withsufiicient pumping throughout for removing the sublimed water vaporwhile maintaining the required vacuum pressure (approximately 1 mm. Hg).The steam ejector evacuation system will also provide sufiicient pumpingspeed throughout to permit the bleed-in of inert gas or air, as throughline 61b, which will provide a pressure gradient as well as a drivingforce to accelerate water vapor transport to the evacuation system.

The desiccated particulate solids drop off the returning conveyor belt57b, and fall into the collector trough 62b from which they precipitateto the dual alternating interlocked discharge air locks 63b and 6411which are similar in construction to the entry air locks describedabove. The desiccated particulate solids can be discharged from the airlocks 63b and 64b directly to a conventional classifier and/or a vacuumor inert gas packaging unit, as desired.

Specific examples of the process may be set out as follows:

Example One 20 gallons of grade A whole milk consisting of approximately10% milk solids and water were introduccd at a pressure of 150 p.s.i.a.and a solution temperature of 170 F. through a discharge nozzle, such asshown at 8a in FIG. 2, at the rate of 0.8 gal./min. and dispersed in theform of a turbulent hollow cone of overlapping sheets or ligaments ofliquid having a cone angle of approximately 55 angle and havingclockwise tangential velocity components. In the apparatus such as thatshown in FIG. 2, the operation was carried on as follows:

The mixed process gas at a ratio of one part liquid nitrogen to threeparts dry compressed air was introduced into a reaction vessel through aring manifold at a temperature of l00 F. and a pressure of p.s.i.a. anda volumetric flow rate of approximately 1100 c.f.h. The mixed processgas was issued through multiple gas jet nozzles protruding from the ringmanifold at a velocity of approximately 650 ft./sec. The jet nozzleswere arranged at an angle to the radius and approximately 30 to thecircumference of the vessel so that a counterclockwise gas spiral wascreated. The high velocity counterclockwise spiralling gas streams weresubsequently tangentially impinged in countercurrent flow upon thedownward clockwise spiralling turbulent hollow cone of overlappingsheets or ligaments of liquid milk. The resultant violent impingement ofthe opposing streams of gas and liquid effected a disintegration of theturbulent hollow cone of liquid into an array of fine water mists anddroplets containing water and milk solids. The fine water mists wereinstantaneously frozen by the high velocity cold gas stream, as well asthe droplets cont-aining water and milk solids.

The fine water mists that were frozen into microcrystalline particles ofice had less mass than the frozen particles containing milk solids andbecame airborne above the spiralling reaction zone. As they wereentrained in the now saturated exhaust gas above the re action zone andtransported to anexhaust duct, as shown at 11a, they served as nucleifor homogenous nucleation of water vapor (in the now warmer saturatedgas) which condensed upon the outer periphery of the coldermicrocrystalline particles of ice throughout its transport by the gasstream to the aforesaid exhaust duct. To summarize, a small percentageof the water removed in the stage two reaction vessel was in the form ofwater vapor which saturated the process gas, while the greatestpercentage of water removed was in the form of microcrystallineparticles of ice which were also entrained in the saturated exhaust gasand were constantly growing by condensation of water vapor on theirouter periphery while they are being separately removed from the vessel.

Simultaneously (during the above operational phenomena), the dropletscontaining water and milk solids were being frozen into particulatesolids (and ice). As these droplets at a temperature of approximately170 F. were being violently agitated in the F. gas stream in thereaction zone, their surface was first cooled, then the outer peripherywas frozen and during the instant the surface was cooling there was amigration of the warmer water and some solids to the outer (colder)periphery of the droplet. This accounted for the partial desiccation ofthe frozen particulate solids interior and the concentration of solid-sand ice at their outer periphery. There was also some violent release ofentrained warmer air escaping from the interior of the droplet and/orfrozen particulate. This escaping gas blew vents or cracks in the frozenparticulates outer periphery effecting greater particle porosity.

The concentration of water (ice) at the outer periphery of the frozenparticulates, and the existence of vents, cracks and/ or blow-holes atthe outer periphery was verified by running separate tests usingsolutions of 20% and 50% of the hexahydrate of cobaltous chloride andwater to simulate a liquid food product during the test runs. Thechloride is blue when anhydrous and pink hydrated, the pure water beingwhite (ice) when frozen. When the frozen particulates issued from thereaction vessel and were examined under a cold stage microscope onecould readily detect the outer ice layer (white) of the particulatesover the frozen eutectic (pink) and the desiccated interior portionswhich were blue. The vents, cracks and blow-holes were also in evidence.These test runs confirmed that the frozen particulate solids had apartially desiccated interior and a higher concentration of ice andsolids at the outer periphery. The white outer ice layer confirmed thehomogeneous nucleation which occurs while the frozen particles wereentrained in the saturated gas stream and served as nuclei for thecondensation of water vapor upon their outer periphery. Subsequentexamination of the trapped exhaust gas issued during these testsconfirmed the removal of microcrystalline particles of ice (white) Withonly occasional particles containing the pink eutectic which indicatedthe presence of solids.

Simultaneously (during the above operational phenomena) the more massivefrozen particulate solids were migrating towards the product removalvalve, such as shown at Ma. Those particles with insufficient mass toovercome the uplift of the process gas in the reaction zone becameairborne and were returned to the reaction zone area. During this periodthey served as nuclei for homogenous nucleation of water vaporcondensing on their surface and also, as they reentered the reactionzone they became wetted and served as nuclei for heterogenousnucleation. That is, other smaller particulate solids were impinged upontheir wetted surfaces and frozen thereto,

thereby increasing the frozen particulate solids mass until finally itwas sufiicient to overcome the updraft of the saturated gas in thereaction zone and fell to the lower, more quiescent zone where it wasremoved separately (from the saturated exhaust gas and its entrainedmicrocrystalline particles of ice) via the product removal valve.

The frozen particulate solids of milk and ice removed via the productremoval valve of vessel averaged 80 F. temperature and had less waterthan the original milk. The water was removed in the form of water vaporand microcrystalline particles of ice entrained in the saturated exhaustgas which was separately removed via the exhaust duct. The remainingwater was predominant as ice at or near the outer periphery of thefrozen particulate solids which averaged 650 microns particle size. Thefrozen particulates were homogenous and featured a partially desiccatedinterior.

The frozen particulate solids of ice and milk featuring 15% less water(ice) and the other product characteristics described above were issuedinto a vacuum vessel, such as shown at 58, and deposited in a thin layerupon the conveyor belt. The conveyor belt was continuously moving withinterrupted motion, thereby effecting a continual tumbling and forwardprogress of the frozen particulate solids towards and through theradiation zone while they were exposed to the vacuum environment of 1mm. Hg pressure. The heat for sublimation was supplied by the selectedwavelength radiator which emitted approximately 95% of its radiationbetween 0.9 and 1.3 microns wavelength. This wavelength of radiationreadily penetrated the milk solids. The ice at the surface of the frozenparticulate solids was opaque to this wavelength of radiation andreadily absorbed the radiation which served as heat for sublimation ofthe ice. As the particles tumbled on the moving conveyor belt, they werecontinuously exposing new ice surfaces to the radiator. As the surfaceice was sublimed to water vapor, a maximum of radiation could still beapplied without scorching the organic milk solids (since the radiationat the specified wavelength passed through the exposed milk solids).This was of great importance as the ice front, receded into the interiorof the frozen particulate and radiant heat was still supplied at amaximum rate.

As the ice front receded the escaping water vapor had ready access tothe vacuum environment through the various vents, cracks and lblow-holespreviously described. This ready access to the vacuum was far moreexpeditious than having the sublimed water vapor diffusing only throughthe previously dried portion of milk solids. As the water vapormolecules escaped from the particulates surface they were impinged byand driven towards an evacuation .port, such as shown at '60, by a highvelocity stream of bleed-in driver gas which was expanded into thevacuum vessel via a gas line 61 as a controlled leak. The expanded'bleed-in or leaked in driver gas provided a driving force to acceleratetransport of the sublimed water vapor to the evacuation system ratherthan depending upon the random motion of water vapor moleculeseventually immigrating from the particles surface to the evacuationport. An added benefit of the driver gas was that it reduced theproportion of water vapor molecules returning to and reentering theparticulate, as is common in the later stages of freeze drying.

The evacuation system provided sufficient pumping speed to maintain 1mm. Hg vacuum pressure at the particulates surface after introduction ofthe nitrogen driver gas, thus establishing a pressure gradient withinthe vacuum vessel and from the particle surface to the vacuumenvironment.

The importance and effectiveness of the selected wav length radiator wasverified during separate tests wherein common infra-red radiation, assupplied by a comm-on infra-red quartz tube element, was radiation tothe frozen particulate solids under the same conditions and with thesame type particles as were heated by the radiation between 0.9 and 1.3microns wavelength. The product was scorched with the common infra-redradiator and was not scorched by the selected wavelength radiator whenboth were radiating at an identical constant rate of output kw. When thecommon in f-raared lamps output kw. was cut back to prevent scorching,it took considerably longer to process the particulates than with theselected wavelength radiator.

The importance and effectiveness of the bleed in gas was also verifiedin a similar manner during further separate tests. Final desiccation ofthe frozen particulates was effected much more rapidly when the bleed indriver gas was employed.

The importance of tumbling the frozen particulates on the movingconveyor belt as it passed through the radiation zone was also verifiedby separate tests. It took a considerably shorter period of time toachieve final desiccation when the particulates were constantly tumbledor agitated and presenting new surfaces to the radiator.

The importance and effectiveness of having the particulates exhibit theproperties and characteristics as previously described when they issuedfrom the reaction vessel was also verified in separate tests. It tookconsiderably longer .to achieve final desiccation on particles that hadmerely been frozen by spraying the liquid milk into a cold gasenvironment and not affecting any water removal or concentration ofsolids and ice at the outer periphery of the particulates or having apartly desiccated interior of the frozen particulates prior toprocessing them through the vacuum vessel (58a).

The final end product removed from the vecuum vessel can "best bedescribed as desiccated, extremely porous, homogenous, very solublespherically particulate milk solids. The average particle size wasapproximately 650 microns. The moisture remaining was approximately0.5%. The particles were very hygroscopic and readily reconstituted incold water. There was no detect-able loss and/ or change of flavor andaroma of the reconstituted 20 gallons of skim milk consisting ofapproximately 9% milk solids and 91% water were processed through areaction vessel, such as that shown at 912 in FIG. 3 under identicalconditions to those previously described in Example One. The frozenparticulate milk solids issued from the vessel via a product removalvalve (14b) feature substantially identical properties andcharacteristics as the frozen whole milk solids similarly removed inExample One.

The frozen particulate solids of ice and milk featuring 15% less water(ice) and the other product properties and characteristics describedabove were then processed to a fluidized bed vessel (75) via the productremoval valve, which was inserted in the ejector chamber section of aconvergent-divergent manifold, such as that shown at 35b. The frozenparticulates were entrained by high velocity cold gas expanding from adivergent ejector nozzle' (3-212) that was also positioned within theejector chamber of the convergent-divergent manifold. The propellinghigh velocity gas jet stream at a temperature of 20 F. expanding intosaid ejector chamber was converting its pressure energy into velocityenergy as it came in contact with and entrained the definite mass offrozen particulate solids of milk and .ice at a temperature of 80 F.issuing into said ejector chamber from the produet removal valve. Thegas imparted to this mass a portion of its own velocity by beingdecelerated and most of its heat energy by exchange with thesuper-cooled particulate mass, effecting some evaporation of the ice onthe particles outer surfaces, and the release of water vapor which wasthen entrained with the gas flow. The resultant combined total massentered the convergent-divergent section of the manifold (3511) whereits velocity energy was, in greater part, again converted into pressure(and heat energy), thereby effecting further evaporation of theentrained particles surface ice. The higher pressure attained permittedthe resultant total mass to be discharged via the divergent entrance tothe fluidized bed reaction vessel through a grid at the lower portion ofthe vessel and thence into the heated multiple honeycomb (hexagonal incross section) column section spaced above the grid. The combined coldgas and particle stream became decelerated and fluidized in the heatedhoneycomb column structure, and exchanged heat with the heated walls ofthe honeycomb structure which were maintained at a temperature of 375 F.and provided the heat for evaporation of the ice predominant at theouter periphery of the frozen particles as they were lifted andviolently agitated by the rising stream of cold process gas. Since theparticles were not bonded together, they moved further apart, opening upthe interstices to allow passage of the gas fluid. Simultaneously theagitated frozen particles were constantly circulating and intermittentlyand momentarily contacting the heated honeycomb walls effecting rapidevaporation from the ice surface of the particles. Also, simultaneouslythe cold process gas was warmed from 20 F. to 32 F. as it passed throughhoneycomb columns and the interstices between the particulates,

thereby enabling the gas to carry a greater proportion of water vaporbefore becoming saturated. As a result of the intermittent momentarycontact with the heated walls, evaporation from the particles icesurface remained at the highest or constant rate drying period. Eventhough the frozen particulates came into momentary contact with the heatwalls they were not scorched since they were supported in the cold gasstream. a

As the ice was evaporated from the frozen particulates they had lessbulk density and became airborne, so that they were carried upwardly inthe fluidized bed vessel and were removed with the saturated exhaust gas(as a temperature of 32 F.) via a cyclone, such as shown at 7 9, whereinthe particles were separated from the gas with the gas flowing upwardlyout of the cyclone to exhaust and the particulates passing outwardlyfrom the bottom of the cyclone.

The milk particles separated and removed from the cyclone were found tohave approximately 20% of their original water remaining in the form ofice. The saturated exhaust gas was then processed through a commercialdryer and heated from 32 F. to 59 F. which doubled its moisture carryingcapacity. It was then recirculated to an identical second manifold, suchas shown at 3512, and a second vessel, such as shown at 75. Meanwhilethe particles issued from the cyclone were reissued into the aforesaidsecond manifold and vessel and reprocessed as previously described abovewith the dry gas now at a temperature of 59 F. The final end productremoved from the second vessel and second cyclone were found to haveless than 5% water remaining which was sufficient dehydration for thedry skim milk. This final end product exhibited identical productproperties and characteristics as that end product previously describedin Example One.

Example Three 20 gallons of grade A whole milk consisting ofapproximately 10% milk solids and water was processed through a reactionvessel, such as that shown at 9b in FIG. 3, and a fluidized :bed andcyclone under identical conditions to those described in ExampleTwoexcept that the frozen milk particulates featuring 20% water (ice)remaining as they passed from the cyclone. These particles were issueddirectly into a vacuumradiationsublimation vessel, such as that shown at58b in FIG. 3 and processed in an idenitcal fashion to that previouslydescribed in Example One. The final desiccated product issued from thevacuum vessel was found to have 0.45% water remaining and exhibitedsimilar properties and characteristics as the desiccated whole milksolids previously described in Example One.

Example Four 20 gallons of skim milk was processed under identicalconditions and in a similar manner as that previously described inExample Two except that the heated honeycomb column walls and the vesselwere inclined at an angle of 45. This increased the incidence of contactbetween the fluidized frozen particles and the heated honeycomb wallsand simultaneously facilitated the introduction of a large-r volume ofprocess gas which in turn permitted removal of a larger volume of watervapor in a given time with a given flow rate of particulates.

The end product issued from the cyclone was identical to that previouslydescribed in Example Two. However, only 75% as long a time was requiredto effect the final desiccation.

Example Five 20 gallons of skim milk was processed under identicalconditions and in similar manner through a reaction vessel, such as thatshown at =9 in FIG. 1, under identical' 23 e-rties and characteristicsas the frozen whole milk solids similarly removed in Example One.

The frozen particulate solids of milk and ice (with 15% of the waterremoved) were discharged via the valve 14 into the ejection chamber 35,as indicated in FIG. 1, wherein they were entrained by a nitrogen gasstream at 25 F. temperature, expanding from the divergent eject-ornozzle 32 at approximately 65 -ft./ sec. velocity. The gas streamimparted its own velocity upon the frozen particles and most of its heatenergy by exchange with the frozen particles, thereby effectingsublimation of the ice on the particles outer periphery and the releaseof water vapor which was also entrained. The resultant combined totalmass, at the resultant velocity, entered a convergentdivergent diffusersection, such as shown at 36, where its velocity energy was, in greaterpart, converted into friction-pressure (and heat energy), therebyeffecting further sublimation. The higher velocity attained permittedthe resultant combined total mass to be discharged to a higher pressurecyclone drying chamber, such as that indicated by the numeral 37 in FIG.1, where it was impinged by, and entrained by, a nitrogen gas stream at30 F., expanded from a divergent ejector nozzle (34) at approximately650 ft/sec. velocity. The combined turbulent streams were then convergedat the conical lower portion of the drying chamber and discharged intoquiescent conical exhauster separator (38). The dried particles,containing about 6.0% moisture, precipitated to the lower portion andwere removed via a rotary product valve (39), while the water vapor andgas stream and any entrained fine product dust were exhausted via a duct4-0 and blower 48 to electrostatic p-recipitators 50 and gas recoverysystem 52 and 53.

The final product, containing 15% moisture, was highly porous,hygroscopic, and was readily reconstituted into skim milk.

Example Six 20 gallons of reconstituted whole dry milk concentrate,consisting of 2 parts Wat-er to one part of dry milk solids, weredischarged at a pressure of 120 psi. and a temperature of 155 F. throughthe discharge nozzle in the apparatus as shown in FIG. 1, as describedin Example Five, except that the nitrogen gas from the jets had atemperature of 135 F., a pressure of 95 p.s.i., and a velocity ofapproximately 650 ft./sec. Also, in the second stage where the materialwas passed into the ejection chamber, the nitrogen gas had a temperatureof 30 F. and a velocity of approximately 650 ft./s-ec. and the nitrogengas expanded into the cyclone drying chamber had a. temperature of 32 F.and a velocity of approximately 650 it/sec.

In the final step, the frozen particle solids were passed into a vacuumvessel maintained at a pressure of 1 mm. Hg and arranged substantiallyas shown in FIG. 2. The process carried on therein exposed theparticulate solids :0 a selected wavelength radiation of 1.3 micronswave- .ength and a stream of dry nitrogen gas at a temperature of 70 F.and a velocity of approximately 700 ft./sec. which was expanded into thevacuum vessel to provide a driving force to accelerate transport of thesublimed water vapor to the evacuation system. The evacuation iystemprovided sufiicient pumping speed to maintain 1 11m. Hg pressure in thevacuum vessel after introduction of the nitrogen driver gas. The finalmoisture content was 0.56%.

Example Seven 20 gallons of whipping grade cream were run as deacribedin Example One except that the liquid cream temperature was 150 F. andpressure was 125 p.s.i.a., and the mixed process gas temperature was 200F. and issued through the ring manifold at 95 p.s.i.a. The desiccatedparticles sizes averaged 500 microns and exhibited similar productproperties and characteristics to those previously described in ExampleOne. The dry cream solids readily reconstituted into whipping gradecream and were subsequently whipped into a full-bodied and fluffywhipped cream.

Example Eight 20 gallons of strained tomatoes containing 25% salt freetomato solids were run, as described in Example One, except that theliquid temperature was 190 F. at a pressure of 95 p.s.i.a. Thedesiccated tomato solids featured identical product properties andcharacteristics to that previously described in Example One. Particlesizes averaged 700 microns. It was also noted that there was no damageto cell structure of the desiccated tomato solids which reconstitutedreadily into a tomato juice drink or a tomato paste as desired.

Example Ten 20 gallons of strained tomatos containing 25 salt freetomato solids were run, as described in Example Two, except thatsuper-cooled carbon dioxide gas was used at a temperature of '90 F.Carbon dioxide gas was also used in the fluidized bed evaporationvessel. Otherwise, the process is substantially as described in ExampleTwo. The final moisture content was 7.5%.

Example Eleven 20 gallons of orange juice concentrate containing 33% ofsolids were processed, as described in Example Five herein, except thatsuper-cooled nitrogen gas and compressed dry air was used in theproportions of 15% nitrogen and air, the temperature of the combineddischarged gas from the jets being F. Further, in the ejection chamber,the gas consisted of 100% air and in the cyclone chamber it consisted of5% nitrogen and air. The final moisture content was 15.3%.

Example Twelve The process was carried out, as described in Example One,except that super-cooled nitrogen and compressed air was used in theproportion of 10% nitrogen and 90% air, the temperature of the combinedgas as discharged from the jet nozzles was 40 F. The final moisturecontent was 1.0%.

While in the foregoing specification, I have set forth certainembodiments of the invention in considerable detail for the purpose ofillustrating the invention, it will be understood that such details ofprocedure and structure may be varied widely by those skilled in the artwithout departing from the spirit of my invention.

I claim:

1. In a process for desiccating organic material in liquid solution, thesteps of: disintegrating said solution into a plurality of droplets,concentrating a predominant percentage of the moisture in each dropletat the exterior thereof in the form of ice to partially desiccate theinterior of each droplet, and subliming the ice from said particles soas to produce a desiccated product.

2. In a process for desiccating organic material in liquid solution, thesteps of: introducing a conically dispersed turbulent spray of solutioninto a confined zone; impinging upon said spray high velocity streams ofdry gas having a temperature below the freezing point of said solutionto disintegrate the spray into liquid mists, droplets of pure water, anddroplets including organic material; simultaneously freezing saiddroplets and mists to form particles of pure ice and frozen particleshaving a nucleus of organic material, While evaporating liquid therefromto saturate said gas and partially desiccate the particles having anucleus of organic material, whereby the predominant percentage of theirremaining liquid is concentrated at the exterior thereof in the form ofice; withdrawing the saturated gas and particles of ice from said zone,and separately withdrawing the ice incrusted, partially desiccatedparticles having a nucleus of organic material from said zone.

3. The process of claim 2 in which the withdrawn gas is freed ofmoisture and ice particles, and is directed in high velocity streamsupon the withdrawn frozen particles for additional removal of moisturetherefrom.

4. The process of claim 2 in which the streams of gas are directedtangentially to the conical spray of solution, and in a spiral directionwith respect thereto.

5. The process of claim 2 in which the partially desiccated iceincrusted particles having a nucleus of organic material are passed in agaseous stream through a constricted zone.

6. The process of claim 5 in which the gaseous stream and ice incrustedparticles are introduced into an enlarged separating zone after passingthrough said constricted zone.

7. The process of claim 2 in which the frozen particles having a nucleusof organic material are maintained under vacuum and subjected to theaction of a radiation source emitting approximately 95% of its radiationbetween 0.9 micron wave length and 1.3 microns wave length.

8. In a process for desiccating organic material in liquid solution, thesteps of: introducing the solution into a first confined zone; impingingupon said solution first high velocity streams of dry gas having atemperature below the freezing point of said solution to disintegratethe solution into liquid mists and droplets; freezing said droplets andrnists to form particles of pure ice and particles having a nucleus oforganic material, while simultaneously evaporating liquid therefrom;withdrawing the resulting vapor and particles of ice from said zone;separately withdrawing the frozen particles having a nucleus of organicmaterial from said zone and entraining them in a second high velocitystream of gas; introducing said second stream of gas and entrainedparticles into a second confined zone having a heated columnar structuretherein; imparting sufiicient velocity to said second stream of gas andentrained particles so as to space said particles from one another, andto cause said particles to intermittently engage said columnar structureand sublime said ice whereby a large percentage of the liquid in saidparticles is removed to saturate said second stream of gas; andwithdrawing said second stream of gas from said second confined zone andseparating said substantially dried particles therefrom.

9. The process of claim 8 including the steps of, removing the particlesof ice from the gas exhausting from the first confined zone, drying saidgas to remove the 'vapor therefrom, and reusing said gas to entrain thefrozen particles issuing from said first confined zone therein.

10. The process of claim Q in which the separated substantiallydesiccated particles are introduced into a third confined zonemaintained under vacuum, and subjected to the action of a radiationsource emitting approximately 95% of its radiation between 0.9 micronwave length and 1.3 microns wave length.

11. In a process for desiccating organic material in liquid solution,the steps of: introducing a conically dispersed turbulent spray ofsolution into a first confined zone; impinging upon said spray incounter-current flow high velocity streams of dry gas having atemperature below the freezing point of said solution to disintegratethe solution into liquid mists and droplets; freezing said droplets andmists to form particles of pure ice and particles having a nucleus oforganic material, while simultaneously evaporating liquid therefrom topartially desiccate the particles having a nucleus of organic materialand concentrate their remaining moisture in the form of ice at the outerportion thereof; withdrawing the resulting saturated gas and particlesof ice from said zone; removing the particles of ice from said saturatedgas; drying said gas to remove the vapor therefrom; separatelywithdrawing the frozen partially desiccated particles having a nucleusof organic material from said zone; redirecting said dried, ice free gasso as to entrain the partially desiccated particlestherein; introducingsaid gas and entrained particles into a vessel with a second confinedzone having a heated columnar structure therein; imparting sufficientvelocity to said gas and entrained'particles so as to space saidparticles from one another; inclining said vessel to increase theincidence of the intermittent engagement of said particles with saidcolumnar structure to sublime said lice whereby a large percentage ofthe liquid in said particles is removed to saturate said gas; andwithdrawing said gas from said second confined zone and separating saidsubstantially dried particles therefrom.

12. In a desiccation process for organic materials including discretefrozen particles having ice incrustations, the steps of introducing saidparticles into a vessel having a heated columnar structure, and passinga dry gas through said vessel at sufficient velocity to suspend saidparticles so that they are spaced from one another, whereby saidparticles are caused to intermittently contact said heated columnarstructure to sublime said ice incrustations and saturate said gas.

13. In a desiccation process for organic materials including discreatefrozen particles having ice incrustations, the steps of introducing saidparticles into a vessel having a columnar structure therein, passing adry gas through said vessel at sufficiently high velocity to suspendsaid particles so that they are spaced from one another and willintermittently contact said columnar structure, heating said columnarstructure whereby sublimation of said incrustations takes place uponcontact of said particles with said columnar structure to saturate saidgas, and separating the dried particles of organic material from saidgas and withdrawing them from said vessel.

14. In a process for desiccating organic material in liquid solution,the steps of: introducing the solution into a confined zone;disintegrating the solution so as to form liquid mists and droplets;freezing said droplets and mists to form particles of pure ice andfrozen particles having a nucleus of organic material, and simul-vtaneously evaporting liquid therefrom; withdrawing the resulting vaporand particles of ice from said zone,

and separately withdrawing the particles having a nucleus of organicmaterial from said zone.

15. In a process for desiccating organic material in liquid solution,the steps of: introducing the solution into a confined zone; impingingupon said solution high velocity streams of dry gas having a temperaturebelow the freezing point of said solution to disintegrate the solutioninto liquid mists and droplets; simultaneously freezing said dropletsand mists to form particles of pure ice and frozen particles having anucleus of organic material while evaporting liquid therefrom;with-drawing saturated gas and particles of ice from said zone, andseparately withdrawing the particles having a nucleus of organicmaterial from said zone.

16. In a process for desiccating organic material in liquid solution,the steps of: introducing the solution into a confined zone;disintegrating and freezing the solution to form frozen particles ofpure ice, frozen particles having a nucleus of organic material, andliquid mists; evaporting said liquid mists and evaporting liquid fromsaid particles to partially desiccate the interior of the particleshaving a nucleus of organic material and to concentrate the remainingliquid in the form of ice at the periphery thereof; withdrawing theresulting vapor and particles of ice from said zone, and separatelywithdrawing the frozen particles having a nucleus of organic materialfrom said zone.

17. In a process for the desiccation of an organic product having wateras a constituent thereof, the steps of dividing said product into aplurality of particles, freezing said particles in a manner so as toconcentrate the Water in the form of ice at the outer periphery of theparticles, passing said particles into a restricted zone maintainedunder vacuum, and subjecting said particles to radiation having a wavelength sufficient to sublime the water from the particles withoutimparting heat to the product.

18. The process of claim 17 wherein the wave length of approximately 95%of the radiation is between 0.9 micron and 1.3 microns.

19. The process of claim 17 wherein different portions of said particlesare subjected. to intermittent radiation.

20. The process of claim 19 wherein said particles are turned to exposedifferent portions thereof to said radiation.

21. The process of claim 17 wherein gas under pressure is admitted intosaid zone to facilitate the sublimation of water from said particles.

22. In a process for the desiccation of organic materials having wateras a constituent thereof, the steps of passing said materials into arestricted zone maintained under vacuum while subjecting said. materialsto radiation in the range of between 0.9 micron wave length and 1.3microns wave length.

23. In a process for the desiccation of organic ma terials having wateras a constituent thereof, the steps of passing materials having adiameter of less than 1,000 microns into a restricted zone maintainedunder vacuum while subjecting said materials to radiation in the rangeof between 0.9 micron wave length and 1.3 microns wave length.

24. In a process for the desiccation of an organic product having aliquid as a constituent thereof, the steps of freezing said product,passing said product into a restricted zone maintained under vacuum, andsubjecting said product to radiation having a wave length sufficient tosublime the frozen liquid from said product without imparting heat tothe product itself.

25. In a desiccation process for organic materials including discretefrozen particles having ice incrustations, the step of passing saidincrusted particles in a high velocity stream of gas through aconstricted. zone at varying relative velocities with respect to saidgaseous stream for frictional contact therewith.

26. The process of claim in which said gas and particles, after leavingsaid constricted zone, are dis charged into an enlarged separation zone.

27. In a desiccation process for organic materials, the steps ofimparting high velocity to frozen organic particles having iceincrustations in a high velocity stream of gas, passing said streamthrough a constricted zone to reduce the velocity of said gas and thenbeyond. said constricted zone into an expanding zone to increase thevelocity thereof, while said particles move at different relativevelocities with respect to said gas into frictional contact therewith.

28. In apparatus for the desiccation of organic materials includingdiscrete frozen particles having water in the form of ice incrustations:a hollow vessel having an inlet and an outlet; a honeycomb structure insaid vessel between said inlet and said outlet and defining a pluralityof columns; means for heating said honeycomb structure; means forintroducing dry gas, together with said particles, into said vesselthrough said inlet, past said honeycomb structure, and out of saidvessel through said outlet to sublime said ice incrustations by engage-I28 ment of said particles with said honeycomb structure; and means forseparating the resulting saturated gas from the resulting driedparticles.

29. Apparatus as defined in claim 28 wherein said vessel is mounted on asupport having an arcuate surface, said vessel having a rounded. portionseated withi said curved portion.

30. In apparatus for the desiccation of liquid containing materials, agenerally vertical vessel having a gas outlet at its top and a solidsoutlet at its bottom, nozzle means for introducing materials into saidvessel in a downwardly directed conical spray, a manifold in anintermediate portion of said vessel below said nozzle, upwardly inclinedjet nozzles carried by said manifold for discharging gas upwardly towardsaid nozzle into said spray, and means for supplying gas at temperaturesbelow freezing and under pressure to said manifold.

31. Apparatus as defined in claim 30 wherein baffles are provided in thelower portion of said vessel and are inclined downwardly and inwardly toform a restricted port communicating with a quiescent zone therebelow.

32. Apparatus as defined in claim 31 wherein a conduit having aconstriction therein communicates with said quiescent zone for receivingmaterials therefrom and which is provided at the end thereof adjacentsaid solids outlet with means for discharging gas into said conduit.

33. In apparatus for the desiccation of liquid containing materials, agenerally vertical vessel having a gas outlet at its top and a solidsoutlet at its bottom, nozzle means for introducing materials into saidvessel in a downwardly directed conical spray, a manifold in anintermediate portion of said vessel below said nozzle, upwardly inclinedjet nozzles carried by said manifold for discharging gas upwardly towardsaid nozzle into said spray, an ejection chamber communicating with saidsolids outlet, nozzle means for introducing dry gas at high velocityinto said ejection chamber to entrain frozen particulates entering intosaid ejection chamber through said solids outlet with said gas, and tocause frictional engagement between said particulates and said gaswhereby partial sublimation of said particulates is effected, means insaid ejection chamber for increasing the frictional contact between'saidgas and said particulates to increase the sublimation of said.particulates, a drying chamber communicating with said ejection chamberand adapted to receive said gas and entrained particulates therefrom,and further desiccation means associated with said drying chamber forsubliming substantially all of the remaining moisture from saidparticulates.

34. Apparatus as defined in claim 33 wherein said further desiccationmeans includes nozzle means in said drying chamber for impinging dry gason said flow of gas and entrained particulates at right angles thereto,and means in said drying chamber for separating said particulates fromsaid gas.

35. Apparatus as defined in claim 34 wherein said further desiccationmeans includes a supplementary ejection chamber communicating with saiddrying chamber and adapted to receive said particulates therefrom,nozzle means for introducing dry gas at high velocity into saidsupplementary ejection chamber to entrain said particulates with saidgas and to cause frictional engagement between said particulates andsaid gas, means in said supplementary ejection chamber for increasingthe frictional contact between said gas and said particulates, and meansfor separating said particulates for said gas.

36. Apparatus as defined in claim 34 wherein said further desiccationmeans includes an evacuated vessel communicating with said dryingchamber and adapted to receive said particulates therefrom, radiationmeans in said vessel and adapted to emit approximately of its radiationbetween 0.9 micron wave length and 1.3 microns wave length for sublimingsubstantially all of the moisture from said particulates, means forremoving the water vapor from said vessel, and means for separatelyremoving said particulates from said vessel.

37. Apparatus as defined in claim 33 wherein said further desiccationmeans includes a honeycomb structure in said drying chamber defining aplurality of columns, means for heating said honeycomb structure, meansfor imparting suflicient velocity to said gas and entrained particulatesto space said particulates from one another and to move saidparticulates into intermittent engagement with the walls of saidcolumns, means for removing said gas from said chamber and means forseparately removing said particulates from said chamber.

38. In a desiccation process for organic materials including discretefrozen particles having ice incrustations, the steps of introducing saidparticles into a vessel having a columnar structure therein, passing adry gas through said vessel at sufficiently high velocity to suspendsaid particles so that they are spaced from one another and willintenrnittently contact said columar structure, heating said columnarstructure whereby sublimation of said incrustations takes place uponcontact of said particles with said columnar structure to saturate saidgas, inclinin-g said vessel so as to increase the incidence ofcollisions between said particles and said columnar structure, andseparating the dried particles of organic material from said gas andWithdrawing them from said vessel.

39. In a desiccation process for organic materials including discretefrozen particles having ice incrustations, the steps of introducing saidparticles into a vessel having a columnar structure therein, passing adry gas through said vessel at sufficiently high velocity to suspendsaid particles so that they are spaced from one another and willintermittently contact said columnar structure, heating said columnarstructure whereby sublimation of said incrustations takes place uponcontact of said particles with said columnar structure to saturate saidgas, separating the dried particles of organic material from said gasand withdrawing them from said vessel, introducing said withdrawnparticles into a second vessel having a heated columnar structuretherein, and drying and heating said withdrawn gas and passing the samethrough said second vessel at sufiiciently high velocity to suspend saidparticles so that they are spaced from one another, whereby saidparticles are caused to intermittently contact said heated columnarstructure to effect further desiccation of said particles.

40. Fluid bed apparatus comprising: a hollow vessel having inlet meansand outlet means; heat transfer means in said vessel between said inletmeans and said outlet means, said heat transfer means including a wallstructure means within said vessel defining a plurality of columns; gridmeans adjacent to said heat transfer means; means for introducing aparticulate substance into said Vessel through said inlet means; meansfor fluidizing said substance in said heat transfer means; means formaintaining a temperature dilference between said heat transfer meansand said substance including means for heating said wall structuremeans; and means for removing said substance from said vessel throughsaid outlet means.

41. Fluid bed apparatus as defined in claim 40 wherein said grid meansis spaced below said wall structure means.

42. Fluid bed apparatus as defined in claim 40 wherein the ratio ofcolumn diameter to the height of said wall structure means is constantthroughout said vessel.

References Cited by the Examiner UNITED STATES PATENTS 1,104,920 7/1914Osborne 34-5 1,213,887 1/1917 Krause 261-791 1,976,204 10/1934 Voorbees34-5 2,020,719 11/ 1935 Bottoms 62-74 2,083,072 6/1937 Lindsey 62-742,413,420 12/1946 Stephanofi 34-10 2,471,035 5/1949 Hurd 34-92 2,533,12512/1950 Levinson 34-5 2,657,473 11/ 1953 Montgomery 34-57 2,659,98611/1953 Hink 34-5 2,668,364 2/ 1954 Colton 34-5 2,731,731 1/1956 Hink eta1. 34-5 2,813,350 11/1957 Berger 34-5 2,911,730 11/1959 Schaub et a134-57 2,921,383 1/1960 Morris 34-57 2,931,711 4/1960 Walker 34-573,019,179 1/1962 Hoppe 34-5 3,024,117 3/1962 Barlow 62-58 3,087,2534/1963 Wulf 34-57 References Cited by the Applicant UNITED STATESPATENTS 2,083,072 6/1937 Lindsey.

WILLIAM J. WYE, Primary Examiner.

ROBERT A. OLEARY, Examiner.

W. E. WAYNER, Assistant Examiner.

1. IN A PROCESS FOR DESICCATING ORGANIC MATERIAL IN LIQUID SOLUTION, THESTEPS OF: DISINTEGRATING SAID SOLUTION INTO A PLURALITY OF DROPLETS,CONCENTRATING A PREDOMINANT PERCENTAGE OF THE MOISTURE IN EACH DROPLETAT THE EXTERIOR THEREOF IN THE FORM OF ICE TO PARTIALLY DESICCATE THE